1. Field
Embodiments of the invention relate to electronic systems, and more particularly, to phase synchronization in radio frequency transmitters in electronic systems.
2. Description of the Related Technology
Certain electronic systems can have multiple transmission paths for transmitting signals. In certain applications, phases of such signals need to be known and/or synchronized for the operation of the system. For example, a wireless communications system can have beam-forming capability by having multiple antenna elements. Such multiple antennas can be provided with signals having known phases, and such signals are added or subtracted to form a beam in a desired direction. Other wireless communications systems may use multiple antenna elements to increase a link margin. In such systems, aligning the phases of transmitted signals is desirable.
Conventional multiple transmission path systems can include a single local oscillator shared for generating signals for multiple transmission paths. However, sharing a single local oscillator can be undesirable or unfeasible in certain applications. For example, a system may require more transmitters than can be included on a single integrated circuit. As another example, in direct conversion transmitters, sharing a single local oscillator is undesirable because routing a carrier frequency signal on a printed circuit board is likely to result in carrier leakage at an output of the transmitter. Because of problems associated with sharing a single local oscillator, some transmitters include two or more integrated circuits with separate local oscillators. In such transmitters, it can be desirable to determine and/or align phases of signals generated using such separate local oscillators.